Just to add my two cents' worth - this dialog pops up for me simply when copying a cell's contents (Ctrl+C) - no dragging/dropping involved at all. All I want to do is copy the cell's text so that I can then paste it into another
application.
What I found was that the dialog isn't totally meaningless/redundant though - because on trying to paste the contents into the other application, I find that the clipboard is blank. So the dialog is misleading - the clipboard
can be emptied, and indeed it is emptied each time - but it's not replaced by the cell's text.
The only way for the copy operation to work successfully is to dismiss the dialog and re-do the Ctrl+C, but sometimes it takes two or three attempts before the copy succeeds without the annoying dialog popup!
Following BorisGR's suggestion, I closed down ZoneAlarm and was amazed that it seemed to fix the issue. I say 'seemed to' because eventually it came back, indicating that it's not a permanent fix, and may have only been coincidental.
For the record, I'm using Office 2010 Home & Student, with Windows 7 Home Premium SP1. I apply all critical updates as they become available.
It was easy to find this thread by googling for the error - but totally unbelievable that it's so many years old, with absolutely no input from MS (on their own forum!) and still no solution.